Dendrimers are highly branched, often spherical molecules in which branches may terminate at charged amino groups that radiate from a central core molecule. Amine-terminated dendrimers have a high density of positively charged amine groups on the surface, such as with PAMAM dendrimers. Due to controlled chemical synthesis, dendrimers have a very precise size and defined shape.
PEHAM dendrimers are related to PAMAM dendrimers but differ in at least one or more of the following characteristics: PEHAM dendrimers show increased thermal stability, more rapid building of surface functionality with increased molecular weight at lower generations thereby reducing costs to make, narrow polydispersity, increased interior void volume, have interior functionality and/or extender groups in the branch arms. These PEHAM dendrimers are described in U.S. Ser. No. 10/594,776, filed 20 Apr. 2005 (published as US 2007/0244296 on Oct. 18, 2007) and U.S. Ser. No. 11/630,044, filed Dec. 21, 2005 (published as US 2007/0298006 on Dec. 27, 2007). Although agricultural use is mentioned generally, there are no specific examples to such use.
It is known that various desired active moieties that are used in agriculture lose effectiveness or require repeated application due to various environmental conditions. The following references discuss some of these issues. When a plant is treated with an active moiety in a carrier, such as spraying it on the plant leaves, the problems observed are uptake and translocation of the desired active moiety or photodegradation of the active. Various attempts have been used to minimize such results such as by adding a surfactant such as Ethylan™ TU [Baker, Edward A., et al., Pestic. Sci. 34, 167-182 (1992)], or an organosilicone surfactant [Stevens, Peter J. G., et al. Pestic. Sci. 38, 237-245 (1993)], or Tinopal™ [Reddy, N. P., et al., Pest Manag. Sci. 64, 909-915 (2008)]. Other approaches concern improving retention on the leaves by adding cuprous oxide and copper oxychloride with a dispersing agent [Large, E. C. et al., Annals of Applied Biol., 33(1), 54-63 (1945), improving local distribution on the leaves by water [Hislop, E. C. et al., Ann. Appl. Biol. 66, 89-101 (1970)], penetration of intact leaf cuticles by various herbicides was measured and found low for several actives [Baker, Edward A., Pestic. Sci. 29, 187-196 (1990)], and imazaquin spray retention, foliar washoff and runoff losses under rainfall conditions was determined which was quite high [Reddy, Krishna N., et al., Pestic. Sci. 48, 179-187 (1996)].
Additionally, UV light causing photodegradation of the active has been studied to try to minimize this effect on loss of active efficacy by several groups, such as to protect amphotericin B [Tufteland, Megan L. et al., Pest Manag. Sci. 65, 624-628 (2009)], rimsulfuron [Scrano, Laura et al., Pestic. Sci. 55, 995-961 (1999)], fenarimol [Sur, Nivedita et al., Pest Manag. Sci. 56, 289-292 (2000)], flucythrinate [Chattopadhyhya S. et al., Pestic. Sci. 31, 163-173 (1991)], phosalone [Walia, S. et al., Pestic. Sci. 25, 1-9 (1989)], fluchloralin [Saha, Tapas et al., Pest Manag. Sci. 58, 179-182 (2001)], flumioxazin [Kwon, Jeong-Wook, et al., Pest Manag. Sci. 60, 939-943 (2004)], bensulfuron-methyl [Si, You-Bin, et al., Pest Manag. Sci. 60, 286-290 (2003)], benzoylphenylurea [Marsella, Adam, et al., Pest Manag. Sci. 56, 789-794 (2000)], and vinclozolin [Schick, Bernhard et al., Pestic. Sci. 55, 1116-1122 (1999)]. A method is to shield the active from UV such as by nanoparticle carriers of hollow silica nanoparticles [Li, Zhu-Zhu et al., Pest Manag. Sci. 63, 241-246 (2007)], using absorber compounds [Hussain, Manzoor et al., Pestic. Sci. 28, 345-355 (1990)], glufosinate [Kocher, Helmut et al., Pestic. Sci. 37, 155-158 (1993)], and 2-propanol and methyl 12-hydroxystearate [Schwack, Wolfgang et al., Pestic. Sci. 40, 279-284 (1994)].
U.S. Pat. No. 6,939,831 describes the use of dendrimers having 2-20,000 phosphorous to nitrogen bonds with active moieties in agriculture. This composition is always a gel composition, which limits its method of application.
These known decreases in the usefulness of an agricultural active moiety cause the requirement for repeated application of the active moiety to the plant, which adds costs for these repeated applications and environmental issues for the runoff or soil retention of the agricultural active moiety.
Clearly, a way to deliver active moieties to plants, while increasing the solubility and penetration of the active moiety, reducing the amount of active to apply or avoiding repeated applications to lower the environmental impact, is desired.
Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one of ordinary skill in the art. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims.